Motor-operated compressor

ABSTRACT

An electric compressor includes a main housing including a motor chamber. The motor chamber includes a driving motor. The compressor includes a frame fixed to one end of the main housing, a first scroll supported by one side surface of the frame, and a second scroll provided between the frame and the first scroll. The second scroll, supported by the frame, makes an orbiting motion upon receiving a rotational force from the driving motor. The second scroll also forms a compression chamber with the first scroll and a back pressure space with the frame. A rear cover coupled to the main housing forms a discharge space with the first scroll. A back pressure flow channel extends through the first scroll and the frame to guide a refrigerant and oil from the compression chamber to the discharge and back pressure spaces. The compressor also includes a plurality of decompression portions.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2018-0088121, filed on Jul. 27, 2018, the contents of which are incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a scroll type motor-operated compressor.

2. Background of the Invention

Generally, compressors for compressing a refrigerant in automotive air conditioning systems have been developed in various forms. Recently, motor-operated compressors (or electric compressors) driven by electricity using motors have been actively developed as automotive parts tend to become electronic/electric components.

A scroll compression method suitable for a high compression ratio operation is mainly applied to electric compressors. In a scroll type electric compressor (hereinafter, referred to as an ‘electric compressor’), a motor unit formed as a rotary motor is installed inside a closed casing, a compression unit including a fixed scroll and an orbiting scroll is installed on one side of the motor unit, and the motor unit and the compression unit are connected by a rotary shaft so that a rotational force of the motor unit is transmitted to the compression unit.

As disclosed in the patent document Japanese Patent Laid-Open Publication No. 2014-125957], in the related art electric compressor, a suction chamber forming a motor chamber and accommodating a sucked refrigerant and oil, a discharge space accommodating the refrigerant and oil discharged from a compression chamber and forming a sort of oil separation space, and a back pressure space accommodating oil in a mist state (hereafter, referred to as a ‘gas oil’) separated from the refrigerant in the discharge space and pressing an orbiting scroll toward a fixed scroll by pressure of the gas oil.

In the above-described related art electric compressor, a back pressure flow channel is formed in a fixed scroll (and/or the main frame) so that gas oil is supplied to the back pressure space from the discharge space. Here, a decompression device is provided in the back pressure flow channel to regulate pressure of the back pressure space by reducing pressure of the gas oil supplied to the back pressure space.

However, since the decompression device of the related art electric compressor as described above is provided at one point of the back pressure flow channel, a decompression effect may be reduced. Furthermore, the related art decompression device is configured by inserting a component such as an orifice or a spiral bolt in the middle of the back pressure flow channel, and thus, the length of a decompression flow channel may be limited. As a result, it is difficult to optimize the size of the decompression flow channel, which makes it difficult to maintain the back pressure space at an appropriate pressure. Particularly, in case where a CO₂ refrigerant is applied to form a discharge pressure of 100 bar or higher, a decompression effect with respect to the gas oil is further lowered compared with a case where another refrigerant (e.g., R134a or R410a) is applied, having a greater difficulty in appropriately maintaining pressure of the back pressure space.

In addition, in the related art decompression device, since the length of the decompression flow channel is limited, the size of the decompression flow channel is reduced to be small to secure a decompression rate. However, as the size of the decompression flow channel is reduced to be small, the decompression flow channel may be clogged with a foreign object. If the decompression passage is clogged, oil shortage occurs in a sliding portion to increase frictional loss or degrade performance of the compressor, or major components of the compressor may be damaged due to burning.

Further, in the related art decompression device, additional components such as an orifice or a spiral bolt are additionally provided in the back pressure flow channel to form the decompression flow channel, which, however, increases the number of components for constituting the decompression device to increase manufacturing cost.

SUMMARY OF THE INVENTION

Therefore, an aspect of the detailed description is to provide an electric compressor in which a decompression device is configured in multiple stages to maintain a back pressure space at an appropriate pressure.

Another aspect of the detailed description is to provide an electric compressor in which a length of a decompression flow channel is increased to increase a decompression effect with respect to gas oil.

Another aspect of the detailed description is to provide an electric compressor in which a decompression effect with respect to gas oil is increased even in case where a high pressure refrigerant such as a CO₂ refrigerant is applied.

Another aspect of the detailed description is to provide an electric compressor in which a decompression effect with respect to gas oil is increased even without forming a decompression flow channel to be excessively narrow in size.

Another aspect of the detailed description is to provide an electric compressor in which oil may be smoothly supplied to a sliding portion by preventing a phenomenon in which a decompression flow channel is clogged by a foreign object.

Another aspect of the detailed description is to provide an electric compressor in which a structure of a decompression device is simplified and the number of components constituting the decompression device is reduced to lower manufacturing cost.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, an electric compressor includes: a decompression portion, which is to reduce pressure of a gas oil, provided in the middle of a back pressure flow channel guiding the gas oil separated from a refrigerant discharged from a compression chamber formed between a first scroll and a second scroll to a back pressure space, wherein the decompression portion is formed to have multiple stages.

Here, the decompression portion may be formed at a gasket sealing two members.

Also, the decompression portion may be formed at a plate supporting a scroll which makes an orbiting motion, among the first scroll and the second scroll, in an axial direction.

The decompression portion may be further formed at a discharge passage allowing the inside and outside of the back pressure space to communicate with each other.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, an electric compressor includes: an electric compressor includes: a main housing forming a motor chamber to communicate a driving motor; a frame fixed to one end of the main housing; a first scroll supported by one side surface of the frame; a second scroll provided between the frame and the first scroll and supported by the frame, making an orbiting motion upon receiving a rotational force from the driving motor to form a compression chamber with the first scroll, and forming a back pressure space with the frame; a rear cover coupled to the main housing to support one side surface of the first scroll and forming a discharge space with the first scroll; a back pressure flow channel penetrating through the first scroll and the frame to guide a refrigerant and oil discharged from the compression chamber to the discharge space to the back pressure space; a first decompression portion provided at a first position between the rear cover and the first scroll and reducing pressure of the refrigerant and oil moving from the discharge space toward the back pressure space; and a second decompression portion provided at a second position between the first scroll and the main housing and reducing pressure of the refrigerant and oil moving to the back pressure space through the first decompression portion.

Here, a decompression member having a plate-like shape may be provided in at least one of the first position and the second position, and the decompression member having a plate-like shape may include an inlet communicating with an upstream side back pressure flow channel with respect to a movement path of the refrigerant and oil, an outlet spaced apart from the inlet and communicating with a downstream side back pressure flow channel, and a decompression flow channel connecting the inlet and the outlet and reducing pressure of the refrigerant and oil moving from the inlet toward the outlet.

The inlet, the outlet, and the decompression flow channel may penetrate through the decompression member in an axial direction.

At least any one of the inlet, the outlet, and the decompression flow channel may be a recess formed on one side surface of the decompression member.

The first decompression member positioned at the first position may be a sealing member having a portion positioned between the main housing and the rear cover.

The first decompression member may include a non-metal material.

The first decompression member positioned at the first position may have an outer diameter smaller than or equal to an outer diameter of the first scroll.

A portion of the second decompression member provided at the second position may be a support member positioned between the frame and the second scroll and supporting the second scroll toward the first scroll.

An outer side portion of the second decompression member may be formed as a fixed end fixed between the frame and the first scroll and an inner side portion of the second decompression member may be formed as a free end supporting the second scroll in an axial direction.

Here, at least any one of the first decompression portion and the second decompression portion may be formed as a decompression flow channel having a predetermined cross-sectional area is recessed and formed on at least any one of both surfaces forming the first position or the second position.

Here, at least any one of the first decompression portion and the second decompression portion may be configured as a decompression flow channel is formed in a slit shape on a decompression member provided at the first position or the second position.

Here, a discharge passage communicating between the back pressure space and the motor chamber may be formed at the frame, and a third decompression portion lowering pressure of the refrigerant and oil discharged from the back pressure chamber to the motor chamber may be further provided at the discharge passage.

Also, the third decompression portion may include a decompression member configured as an orifice or a decompression valve inserted into the inside of the discharge passage.

The third decompression portion may have a plate-like shape and provided on one side surface of the frame, and the decompression member forming the third decompression portion may include an inlet communicating with the discharge passage, an outlet provided on one side of the inlet and communicating with the motor chamber, and a decompression flow channel connecting the inlet and the outlet and reducing pressure of the refrigerant and oil moving from the inlet to the outlet.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, an electric compressor includes: a main housing forming a motor chamber to communicate a driving motor; a frame fixed to one end of the main housing; a first scroll supported by one side surface of the frame; a second scroll provided between the frame and the first scroll and supported by the frame, making an orbiting motion upon receiving a rotational force from the driving motor to form a compression chamber with the first scroll, and forming a back pressure space with the frame; a rear cover coupled to the main housing to support one side surface of the first scroll and forming a discharge space with the first scroll; a back pressure flow channel penetrating through the first scroll and the frame to guide a refrigerant and oil discharged from the compression chamber to the discharge space to the back pressure space; and a plurality of decompression portions provided in the middle of the back pressure flow channel at predetermined intervals and reducing pressure of the refrigerant and oil moving from the discharge space to the back pressure space through the back pressure flow channel.

Here, the plurality of decompression portions may have different decompression rates.

A first decompression portion may be provided between the rear cover and the first scroll, a second decompression portion may be provided between the first scroll and the main housing, and a decompression rate of the first decompression portion may be greater than or equal to a decompression rate of the second decompression portion.

A discharge passage communicating between the back pressure space and the motor chamber may be formed in the frame, the discharge passage may further include a third decompression portion lowering pressure of the refrigerant and oil discharged from the back pressure space to the motor chamber, and a decompression rate of the third decompression portion may be smaller than or equal to a decompression rate of the second decompression portion.

Here, the plurality of decompression portions may include an inlet, an outlet, and a decompression flow channel connecting the inlet and the outlet, and the decompression flow channel may be wound at 180° or greater in a direction from the inlet to the outlet.

In the electric compressor according to the present disclosure, since the decompression portions are configured in multi-stages between the discharge space and the back pressure space, gas oil moving from the discharge space to the back pressure space may be effectively decompressed.

Thus, since the pressure of the back pressure space may be reduced to an appropriate pressure, pressure leakage between the scrolls and frictional loss may be suppressed. Also, since the decompression portions are separated in multiple stages and the decompression rates of the decompression portions are appropriately adjusted, pressure of the gas oil supplied to the back pressure space may be reduced to an appropriate pressure, and thus, pressure of the back pressure space may be more appropriately maintained.

Further, since the plurality of decompression portions have the long decompression flow channel, the cross-sectional area of the decompression flow channel may be formed relatively large, thereby preventing the decompression flow channel from being clogged by foreign substances, enhancing reliability of the compressor.

Further, since the decompression portions are formed using existing components such as a gasket or a back pressure plate, the number of components may be reduced, as compared with a case where a separate decompression device is provided, so that manufacturing cost may be reduced.

Further, by providing the discharge passage and the decompression portions between the back pressure space and the suction space, the pressure of the back pressure space may form a dynamic pressure, so that the gas oil may be smoothly supplied to the back pressure space and pressure of the gas oil discharged to the suction space may be further lowered to suppress suction loss.

Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a cross-sectional view of an electric compressor according to the present disclosure;

FIGS. 2 and 3 are an exploded perspective view and an assembled cross-sectional view of a compression unit in FIG. 1;

FIG. 4 is a cross-sectional view taken along line “V-V” in FIG. 3, illustrating a first decompression portion of FIG. 1;

FIG. 5 is a cross-sectional view taken along line “VI-VI” in FIG. 3, illustrating a second decompression portion of FIG. 1;

FIG. 6 is a cross-sectional view illustrating a third decompression portion in FIG. 1;

FIG. 7 is a schematic view for explaining a circulation structure of a refrigerant and oil in an electric compressor according to the present embodiment;

FIGS. 8 and 9 are an exploded perspective view illustrating another embodiment of a first decompression portion according to the present embodiment;

FIG. 10 is a perspective view illustrating another embodiment of a back pressure plate according to the present embodiment;

FIGS. 11A and 11B are cross-sectional views illustrating other embodiments of a third decompression portion according to the present embodiment;

FIG. 12 is a cross-sectional view illustrating another embodiment of a decompression device according to the present embodiment;

FIG. 13 is a cross-sectional view illustrating another embodiment of a first decompression portion and a second decompression portion in an electric compressor according to the present embodiment; and

FIG. 14 is a cross-sectional view illustrating another embodiment of a first decompression portion and a second decompression portion in an electric compressor according to the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an electric compressor according to the present disclosure will be described in detail with reference to an embodiment illustrated in the accompanying drawings.

An electric compressor according to the present disclosure, a part of a refrigerating cycle device for sucking and compression a refrigerant, is a scroll compressor in which two scrolls are engaged to compress a refrigerant. In this embodiment, a high temperature and high pressure electric scroll compressor in which a discharge pressure is 100 bar, specifically, substantially 130 bar, and a discharge temperature is approximately 170° C. using a carbon dioxide (CO₂) refrigerant will be described for example. FIG. 1 is a cross-sectional view of an electric compressor according to the present disclosure.

Referring to FIG. 1, an electric compressor according to the present embodiment may include a casing 101, a main frame 102, a driving unit 103, and a compression unit 104. Also, an inverter unit 200 for controlling an operation of the compressor may be provided outside a front cover 112 (to be described). Accordingly, the inverter unit 200 may be positioned on the opposite side of the compression unit 104 with respect to the driving unit 103. Hereinafter, the inverter unit side will be referred to as a front side and the compression unit side, i.e., the opposite side, will be referred to as a rear side.

The casing 101 may include a main housing 111, a front cover 112, and a rear cover 113.

The main housing 111 has a cylindrical shape in which front and rear ends are open, and the front cover 112 may be coupled to a front end and the rear cover 113 may be coupled to a rear end. A suction space S1 forming a motor chamber may be formed in the main housing 111, and a discharge space S2 may be formed in the rear cover 113, together with a first scroll 140 (to be described).

The driving unit 103, the frame, and the compression unit 104 are accommodated in the suction space S1, and an oil separation portion 116 separating oil from a refrigerant discharged to the discharge space S2 may be installed in the discharge space S2.

An intake port 111 a communicating with the suction space S1 is formed on a side wall of the main housing 111, and an exhaust port 113 a communicating with the discharge space S2 may be formed on a side wall of the rear cover 113. The oil separation portion 116 described above may be installed in the exhaust port 113 a. An oil supply hole 113 b is formed in a lower portion of the rear cover 113 and oil separated by the oil separation portion 116 is mixed with a gas and moves toward the back pressure flow channel F through the oil supply hole 113 b. The back pressure flow channel F includes a first back pressure flow channel 142 a and a second back pressure flow channel 121 a, which will be described later. The first back pressure flow channel 142 a is formed in a scroll side wall portion 142 of the first scroll 140 and the second back pressure flow channel 121 a is formed in a body portion 121 of the main frame 102.

The refrigerant is introduced to the casing 101 through the intake port 111 a and sucked into the compression unit 104 after passing through the driving unit 103 from the front side to the rear side. As the refrigerant discharged into the space S2 from the compression unit 104 passes through the oil separation portion 116, the refrigerant is separated from oil, and the refrigerant separated from oil moves to a refrigerating cycle through the exhaust port 113. Meanwhile, the gas oil in a mist state separated from the refrigerant is stored in the discharge space S2 and supplied to a back pressure space S3 through the back pressure flow channel F (to be described). The structure in which oil is supplied to the back pressure space will be described again together with a decompression device later.

The main body 102 has the body portion 121 formed in an annular disc shape and an edge of the body portion 121 may be supported and coupled between a front surface of the scroll side wall portion 142 of the first scroll 140 and an inner step surface 111 b of the main housing 111. A first sealing member 171 is provided on a bearing surface of the second scroll 150 in contact with a bearing surface of the body portion 121 to seal a thrust bearing surface between the main frame 102 and the second scroll 150.

A back pressure space portion 122 forming the back pressure space S3 is formed at the center of the main frame 102, and a balance weight 136 compensating for imbalance according to an off-centered orbiting motion of the second scroll 150 may be rotatably accommodated in the back pressure space portion 122.

A shaft hole portion 123 protrudes forwards at the center of the back pressure space portion 122 and a shaft hole 124 into which a rotary shaft 135 is rotatably inserted is formed at the center of the shaft bearing portion 123. A main bearing 161 described above is fixedly coupled to an inner circumferential surface of the shaft receiving portion 123 and a second sealing member 172 sealing one side of the back pressure space S3 may be inserted and coupled to an inner circumferential surface of the shaft hole 124. Accordingly, the back pressure space portion 122 is sealed by the first sealing member 171 and the second sealing member 172 to form the back pressure space S3 described above.

The first sealing member 171 and the second sealing member 172 may be formed in a ring shape having a quadrangular, V-shaped, or U-shaped cross-section. The first sealing member 171 and the second sealing member 172 may be formed of a material such as Teflon or engineer plastic. Here, the first sealing member 171 and the second sealing member 172 may be formed of a material having friction coefficient lower than that of the main frame 102 or the second scroll 150 in consideration of friction loss.

Meanwhile, the driving unit 103 includes a stator 131 and a rotor 132, and generates a rotational force for driving the rotary shaft 135. In this embodiment, the stator 131 may be fixed to an inner circumferential surface of the main housing 111 and may have an annular shape to form a cylindrical space therein. The rotor 132 may be spaced apart from the stator 131 in an inner space of the stator 131. The rotor 132 may have a substantially cylindrical shape, and the rotary shaft 135 may be coupled to the center thereof. When power is supplied to the driving unit 103, the rotor 132 and the rotary shaft 135 may rotate together by an interaction between the stator 131 and the rotor 132.

The rotary shaft 135 may be accommodated in the main housing 111 and rotatably supported on the main frame 102. The rear side of the rotary shaft 135 may be supported in a radial direction by the main bearing 161 mounted on the main frame 102. The main bearing 161 may be configured as a deep groove ball baring in which an inner ring is coupled to the rotary shaft 135 and an outer ring is coupled to the main frame 102, and press-fit to the main frame 102.

In addition, a front end portion of the rotary shaft 135 may be supported in the radial direction by a sub-bearing 162 provided at the front cover 112. The sub-bearing 162 may be mounted on a shaft support protrusion 114 formed on an inner surface of the front cover 112. Accordingly, a part of an outer circumferential surface of the rotary shaft 135 may be coupled with the rotor 132 to receive a rotational force generated by the driving unit 103.

Meanwhile, the compression unit 104 may include a first scroll 140, which is a fixed scroll, and a second scroll 150, which is a orbiting scroll. The second scroll 150 is eccentrically coupled to the rotary shaft 135 coupled to the rotor 132 of the driving unit 103 and makes an orbiting motion with respect to the first scroll 140 to form a pair of two compression chambers V including a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the first scroll 140.

The first scroll 140 includes a fixed side disk plate portion 141 having a disk shape, and a scroll side wall portion 142 protruding toward the main frame 102 may be formed on one side of the fixed side disk plate portion 141.

A fixed wrap 143 engaged with the orbiting wrap 152 (to be described later) to form a pair of two compression chambers V may protrude from a central portion of the fixed disk plate portion 141, a suction opening (not shown) communicating with the suction space S1 of the casing 101 may be formed at an edge of the fixed side disk plate portion 141, and a discharge opening 144 communicating with a final compression chamber and the discharge space S2 may be formed at the center of the fixed side disk plate portion 141.

In the second scroll 150, an orbiting side disk plate portion 151 is formed, an orbiting wrap 152 protruding toward the fixed side disk plate portion 141 and engaged with the fixed wrap 143 is formed on one side surface of the orbiting side disk plate portion 151, and a boss recess 153 allowing an eccentric bearing 163 supporting the rotational shaft 135 to be inserted and fixed therein is formed on the other side surface of the orbiting side disk plate portion 151. Accordingly, the second scroll may be coupled with the rotational shaft 135 with the eccentric bearing 163 and the balance weight 136 interposed therebetween so as to be provided with a rotational force.

Meanwhile, a back pressure flow path F allowing the discharge space S2 and the back pressure space S3 to communicate with each other may be formed at the fixed side disk plate portion 151 of the first scroll 150 and the main frame 102. Accordingly, a gas oil separated from the discharge space S2 moves to the back pressure space S3 through the back pressure flow path F to form a back pressure in the back pressure space S3.

In the drawing, reference numeral 180 is a pin-and-ring type anti-rotation mechanism.

The electric compressor according to the present disclosure operates as follows.

That is, when power is applied to the driving unit 103, the rotary shaft 135 rotates together with the rotor 132 of the driving unit 103 to transmit a rotational force to the second scroll 150. Then, the second scroll 150 eccentrically connected to the rotary shaft 135 makes an orbiting motion by an off-centered distance by the anti-rotation member 180 and the compression chamber V continues to move toward a radial center side of the rotary shaft 135 to reduce the volume.

Thus, the refrigerant flows into the suction space S1 constituting a motor chamber through the suction port 111 a and sucked into the compression chamber V. Here, the refrigerant may cool the stator 131 and the rotor 132, while passing through the driving unit 103.

Thereafter, the refrigerant sucked into the compression chamber V is compressed, while moving toward the center side along a movement path of the compression chamber V, and is discharged to the discharge space S2 formed between the first scroll 140 and the rear cover 113 through the discharge opening 144.

Oil of the refrigerant discharged to the discharge space S2 is separated at the discharge space S2 or is separated while the refrigerant is passing through an oil separation portion 116, and the refrigerant is discharged to the refrigerating cycle through the exhaust port 113 a. Meanwhile, the separated oil remains as gas oil in a mist state mixed with a small amount of refrigerant, and the gas oil moves to the back pressure space S3 through the back pressure flow path F described above to form a back pressure. The gas oil in the back pressure space S3 is discharged to the suction space S1 through a discharge passage 125 provided in the main frame 102 and then sucked into the compression chamber V together with a sucked refrigerant. The process is repeated.

Meanwhile, a pressure of the back pressure space, i.e., a back pressure, must be maintained at an appropriate pressure so that a behavior of the second scroll as the orbiting scroll may be stably maintained. If the back pressure is small, the a bearing power for the second scroll is weakened to degrade adhesion with the first scroll as the fixed scroll. As a result, leakage may occur in the compression chamber to increase compression loss in the compression chamber. Meanwhile, if the back pressure is too large, the second scroll may make an orbiting motion, in a state of being in an excessively close contact with the first scroll to increase friction loss.

Particularly, when a CO₂ refrigerant is applied, a discharge pressure rises to about 100 bar or higher, and further, up to 130 bar. Therefore, in the case of the compressor to which the CO₂ refrigerant is applied, a decompression device having a decompression rate higher than that of a compressor to which a general refrigerant described above is applied must be applied.

However, as described above, in the related art decompression device, it is difficult to optimize a size of a decompression flow path and it is difficult to install a plurality of decompression flow paths, so that it may be difficult to maintain an appropriate pressure in the back pressure space. Further, as the length of the decompression flow path is short and narrow, and it may be clogged by a foreign object. Also, since the decompression device is configured as a separate component, a structure thereof may be complicated and the number of components may be increased. Thus, in this embodiment, a plurality of decompression devices are formed, and a plurality of decompression devices may be provided and arranged in multiple stages.

Referring back to FIG. 1 again, the electric compressor according to the present embodiment may include a first decompression portion installed at a first position P1 between the rear cover 113 and the first scroll 140 and a second decompression portion installed at a second position P2 between the first scroll 140 and the main frame 102.

Here, the first decompression portion and the second decompression portion may be formed using plates provided at the first position P1 and the second position P2, or decompression portions may be formed on a surface facing the first position P1 and the second position P2, i.e., a front surface of the rear cover 113 and a rear surface of the first scroll 140 or on a front surface of the first scroll 140 and a rear surface of the main frame, respectively. In the former case, since the decompression portion is formed and assembled to a part such as a gasket or a back pressure plate, processing of the scroll and the frame as core members may be facilitated, and in the latter case, since the decompression portion is formed at an existing member, the part may be replaced with another component, increasing a degree of freedom of design. Hereinafter, an example of forming a decompression portion at a gasket or a back pressure plate will be described first. FIGS. 2 and 3 are an exploded perspective view and an assembled cross-sectional view of the compression unit illustrated in FIG. 1, FIG. 4 is a cross-sectional view taken along line V-V of FIG. 3, illustrating the first decompression portion in FIG. 1, FIG. 5 is a cross-sectional view taken along line VI-VI of FIG. 3, illustrating the second decompression portion in FIG. 1, and FIG. 6 is a cross-sectional view illustrating a third decompression portion in FIG. 1.

As illustrated in FIGS. 2 to 4, the first decompression portion may be formed at a gasket 191 positioned between the main housing 111 and the rear cover 113 and sealing a gap between the main housing 111 and the rear cover 113. For example, an inner side of the gasket 191 according to the present embodiment may be formed of a metal material and an outer side of the gasket 191 may be formed of a non-metallic material and has an annular shape in which a central portion is opened to surround a discharge space. Of course, the gasket may be formed entirely of a non-metallic or metallic material.

An outer side portion of the gasket 191 is positioned between the main housing 111 and the rear cover 113 and is fastened together by a bolt fastening the main housing 111 and the rear cover 113, and an inner side portion of the gasket 191 is positioned between the rear cover 113 and the first scroll 140 and tightly fixed between the rear cover 113 and the first scroll 140. Accordingly, a plurality of bolt holes 191 d are formed on the outer side portion of the gasket 191 and a first decompression portion is formed on an inner side of the bolt holes 191 d, i.e., on an inner side portion of the gasket 191.

The first decompression portion includes a first inlet 191 a, a first outlet 191 b formed at a predetermined distance from one side of the first inlet 191 a, and a first decompression flow channel 191 c communicating between the first inlet 191 a and the first outlet 191 b.

The first inlet 191 a communicates with an oil supply hole 113 b provided at the rear cover 113, and the first outlet 191 b communicates with a first back pressure flow channel provided at the first scroll 140. Accordingly, the gas oil in the discharge space flows into the first inlet 191 a through the oil supply hole 113 b, moves to the first outlet 191 b along the first decompression flow channel 191 c, and moves to a second back pressure flow channel 121 a (to be described later) through the first outlet 191 b.

The first inlet 191 a is formed to have substantially the same inner diameter as that of the oil supply hole 113 b. Therefore, the inner diameter of the first inlet 191 a is formed to be larger than the inner diameter of the first outlet 191 b and is wider than the width of the first decompression flow channel 191 c. The width of the first decompression flow channel 191 c may be substantially equal to the inner diameter of the first outlet 191 b.

In order to increase a decompression effect, the first decompression flow channel 191 c is formed as long as possible. For example, the first decompression flow channel 191 c may have a circular arc shape so as to be wound at least about 180° or greater, preferably, about 270° or greater, from the first inlet 191 a toward the first outlet 191 b.

Meanwhile, the second decompression portion may be formed to be substantially the same as the first decompression portion. The second decompression portion is positioned between the second scroll 150 and the main frame 102 and formed at the back pressure plate 192 formed of a metal material to support the second scroll 150 toward the first scroll 140. Thus, a second inlet 192 a and a second outlet 192 b of the second decompression portion (to be described later) may be formed in a penetrating manner, while a second decompression flow channel 192 c may be formed to be recessed in consideration of an elastic force of the back pressure plate. Of course, in case where the second decompression portion is positioned to be in close contact between the first scroll 140 and the main frame 102 as illustrated in FIG. 3, the second decompression flow channel 192 c may be formed to be cut like the first decompression flow channel 191 c.

For example, the back pressure plate 192 may have an annular shape. An outer side portion of the back pressure plate 192 may be formed as a fixed end tightly fixed between the first scroll 140 and the main frame 102 and an inner side portion thereof may be formed as a free end supporting the second scroll 150. Thus, the second decompression portion may be formed between the fixed end and the free end of the back pressure plate 192 and the second inlet 192 a and the second outlet 192 b (to be described later) may be formed between a front side surface of the a scroll side wall portion 142 of the first scroll 140 and a rear side surface of the body portion 121 of the main frame 102.

The second decompression portion includes the second inlet 192 a, the second outlet 192 b, and the second decompression flow channel 192 c. The second inlet 192 a communicates with the first back pressure flow channel 142 a and the second outlet 192 b communicates with the second back pressure flow channel 121 a. As described above, the first back pressure flow channel 142 a is formed in a penetrating manner on the scroll side wall portion 142 forming a side wall portion of the first scroll 140 in an axial direction or in a tilted direction, and the second back pressure flow channel 121 a is formed in a penetrating manner on the body portion 121 of the main frame 102 in a tilted direction. The first back pressure flow channel 142 a communicates with the oil supply hole 113 b through the first decompression portion to connect the first position P1 and the second position P2, and the second back pressure flow channel 121 a connects the second position P2 and the back pressure space S3. Accordingly, the discharge space S2 communicates with the back pressure space S3 through the first back pressure flow channel (more precisely, including the oil supply hole) 142 a and the second back pressure flow channel 121 a.

The second decompression flow channel 192 c may be formed as long as possible like the first decompression flow channel 191 c to increase a decompression effect. For example, the second decompression flow channel 192 c may have an arc shape so as to be wound at least 180 degrees, preferably, at least 270 degrees, from the second inlet 192 a toward the second outlet 192 b.

Meanwhile, a length L1 of the first decompression flow channel and a length L2 of the second decompression flow channel may be formed according to decompression rates of the first decompression portion and the second decompression portion. For example, as illustrated in FIGS. 4 and 5, when the decompression rates of the first decompression portion and the second decompression portion are the same, the length L1 of the first decompression flow channel and the length L2 of the second decompression flow channel may be equal. In this case, a cross-sectional area of the first decompression flow channel 191 c and a cross-sectional area of the second decompression flow channel 192 c are equal. If the cross-sectional area of the first decompression flow channel and the cross-sectional area of the second decompression flow channel are different, the lengths of the first and second decompression flow channels 191 c and 192 c may be limited to be different from those described above. However, since the cross-sectional areas of the first decompression flow channel 191 c and the second decompression flow channel 192 c are very narrow, it is not easy to set a decompression ratio using the cross-sectional areas of the decompression flow channels. Therefore, it may be advantageous to set the decompression rate using the decompression length of the decompression flow channels.

In another embodiment, the decompression rate of the first decompression portion may be formed larger than the decompression rate of the second decompression portion. In this case, the length L2 of the second decompression flow channel may be formed to be shorter than the length L1 of the first decompression flow channel, or vice versa, although not shown. Also, the length of the first decompression flow channel and the length of the second decompression flow channel may be set to be equal according to the cross-sectional area of the first decompression flow channel and the cross-sectional area of the second decompression flow channel have.

This is the same with the case of a third decompression portion to be described later. For example, in case where the third decompression portion is formed using a decompression plate, the decompression rate may be determined by adjusting a length of the third decompression flow channel. In this case, since a back pressure of the back pressure space S3 is significantly low, as compared with a pressure of the discharge space S2, the length L3 of the third decompression flow channel may be formed to be shorter than the length L1 of the first decompression flow channel or the length L2 of the second decompression flow channel. However, in case where the third decompression portion is formed as an orifice 193 as illustrated in FIG. 3, a decompression ratio may be set by adjusting an inner diameter of the decompression hole 193 a of the orifice 193.

Meanwhile, as the back pressure space S3 is sealed by the first sealing member 171 and the second sealing member 172, a gas oil accommodated in the back pressure space S3 may be stagnated. Then, the gas oil stored in the discharge space S2 may not flow to the back pressure space S3, and thus, oil circulation inside the casing may be insufficient as a whole.

Thus, the main frame 102 according to the present embodiment may be provided with an oil discharge passage 125 allowing the back pressure space S3 to communicate with the suction space S1, which is a motor room. The oil discharge passage 125 forms a passage through which gas oil is discharged from the back pressure space S3 to the suction space S1.

The oil discharge passage 125 may further include the third decompression portion for lowering pressure of the gas oil discharged from the back pressure space S3. The third decompression portion may be configured as an orifice or a decompression valve inserted into the inside of the oil discharge passage 125.

For example, as illustrated in FIGS. 3 and 6, the third decompression portion of the orifice 193 may be inserted into the oil discharge passage 125 provided on a side surface of the back pressure space portion 122 of the main frame 102. To this end, the oil discharge passage 125 may include an discharge recess 125 a formed in a recessed shape on an upper surface of the body portion 121 and a discharge hole 125 b formed to penetrate through the body portion 121 in an axial direction toward an outer side surface of the main frame 102 from the discharge recess 125 a.

The orifice 193 may be inserted and fixed in the middle of the discharge hole 125 b. The orifice 193 may include one or more small decompression holes 193 a. The decompression hole 193 a may be appropriately set in consideration of the decompression rates of the first decompression portion and the second decompression portion as described above.

In the drawing, reference numeral 192 d denotes pin through holes.

The electric compressor according to the present embodiment as described above has the following operational effects. FIG. 7 is a schematic view for explaining a circulation structure of a refrigerant and oil in the electric compressor according to the present embodiment.

As illustrated, a refrigerant discharged from the compression chamber V to the discharge space S2 is separated from the oil in the discharge space S2 or the oil separation portion 116, and the refrigerant is discharged to the refrigerating cycle device and the gas oil separated from the refrigerant remains in a mist stage in the discharge space S2.

This gas oil flows to the first inlet 191 a forming the first decompression portion through the oil supply hole 113 b due to a pressure difference and this gas oil flows from the first inlet 191 a along the first decompression flow channel 191 c. The gas oil is decompressed to a first pressure, while moving along the first decompression flow channel 191 c and the gas oil decompressed to have the first pressure is moved to the first pressure flow channel 142 a through the first outlet 191 b.

The gas oil which is first decompressed by the first decompression portion flows to the second inlet 192 a constituting the second decompression portion through the first back pressure flow channel 142 a. As this gas oil flows along the second decompression flow channel 192 c, it is decompressed to a second pressure, and the gas oil decompressed to the second pressure moves to the second back pressure flow channel 121 a through the second outlet 192 b. The gas oil introduced to the second back pressure flow channel 121 a is supplied, in a state of being decompressed to the second pressure, to the back pressure space S3.

The gas oil filling the back pressure space S3 presses the second scroll 150 in a direction toward the first scroll 140 so that the second scroll 150 is brought into close contact with the first scroll 140, thus restraining the refrigerant compressed in the compression chamber from leaking.

A portion of the gas oil filled in the back pressure space S3 is discharged to the suction space S1 constituting the motor chamber in the back pressure space S3 through the discharge passage 125 provided in the main frame 102. Accordingly, as the discharge space S2 communicates with the suction space S1 via the back pressure space S3, the back pressure space S3 forms a dynamic pressure. Since the back pressure space S3 forms a dynamic pressure, the gas oil separated in the discharge space S2 continuously moves toward the back pressure space S3 and the suction space S1, forming a smooth circulation structure inside the casing 101.

Here, the gas oil discharged from the back pressure space S3 to the suction space S1 is decompressed to a third pressure, while passing through the third decompression portion provided in the discharge passage 125 of the main frame 102, so as to be discharged. Accordingly, the pressure of the gas oil flowing into the suction space S1 from the back pressure space S3 may be lowered to restrain an increase in a specific volume in the suction space S1, whereby suction loss may be lowered.

Thus, as the gas oil moving from the discharge space to the back pressure space is reduced to the first pressure and the second pressure, while passing through the first decompression portion and the second decompression portion, a back pressure of the gas oil filling the back pressure space may be sufficiently reduced. In particular, since the first decompression flow channel and the second decompression flow channel are each formed to extend in a circular arc shape, the gas oil may be more effectively decompressed. Accordingly, frictional loss between the scrolls that may occur when the pressure of the back pressure space is high may be suppressed.

Further, the first decompression portion and the second decompression portion are separately provided, the decompression rates of the first decompression portion and the second decompression portion are appropriately adjusted, and accordingly, pressure of the back pressure space may be optimized.

Even in case where a high pressure refrigerant such as a CO2 refrigerant, as well as a general refrigerant, is applied, pressure of the gas oil supplied to the back pressure space may be reduced to an appropriate pressure.

In addition, since the first decompression flow channel and the second decompression flow channel extend, the cross-sectional area of the decompression flow channels may be relatively wide, and thus, the decompression flow channels may be prevented from being clogged by foreign substances, increasing reliability.

In addition, since the first decompression portion and the second decompression portion are formed using existing components such as gaskets or back pressure plates, the number of components may be reduced as compared with a case where a separate decompression device is installed.

Further, since the discharge passage and the third decompression portion are provided between the back pressure space and the suction space, pressure of the back pressure space may become a dynamic pressure, and thus, the gas oil may be smoothly supplied to the back pressure space and pressure of the gas oil discharged to the suction space may be further lowered to suppress suction loss.

Hereinafter, another embodiment of the first decompression portion in the electric compressor according to the present disclosure will be described. FIGS. 8 and 9 are an exploded perspective view and an assembled major part cross-sectional view illustrating another embodiment of the first decompression portion according to the present embodiment.

As illustrated, the gasket 291 according to the present embodiment may be positioned only between the rear cover 113 and the first scroll 140. Accordingly, an outer diameter of the gasket 291 may be smaller than or equal to an inner diameter of the main housing 111 and may be substantially similar to an outer diameter of the first scroll 140.

Even when the gasket 291 is located only between the rear cover 113 and the first scroll 140 inside the main housing 111, the first decompression portion provided in the gasket 291 may be formed to be the same as that of the previous embodiment. That is, even in this case, the first inlet 291 a, the first outlet 291 b, and the first decompression flow channel 291 c constituting the first decompression portion may be formed at the same position and in the same shape in the gasket 291 as those of the previous embodiment. The first inlet 291 a, the second outlet 291 b, and the first decompression flow channel 291 c may be formed to be the same as those of the embodiment illustrated in FIGS. 2 and 3.

Accordingly, operational effects according to the present embodiment may be similar to those of the embodiment described above. However, in the present embodiment, since the separate sealing member 175 is provided between the main housing 111 and the rear cover 113 in addition to the gasket 291, the decompression portion may be formed using a separate plate like the second decompression portion in the embodiment of FIGS. 2 and 3 described above, in the place of the gasket.

Hereinafter, another embodiment of the first decompression flow channel or the second decompression flow channel according to the present embodiment will be described.

That is, compared with the above-described embodiment in which the first decompression flow channel and the second decompression flow channel are formed in a slit shape on the gasket and the back pressure plate, respectively, in the present embodiment, the first decompression flow channel or the second decompression flow channel is formed in a recessed shape. Hereinafter, the second decompression portion will be described as an example but the first decompression portion may be the same.

FIG. 10 is a perspective view illustrating another embodiment of a back pressure plate according to the present embodiment. As illustrated in FIG. 10, a second inlet 292 a and a second outlet 292 b are formed as holes, and a second decompression flow channel 292 c may be formed as a recess connecting the second inlet 292 a and the second outlet 292 b. Although not shown, the second inlet 292 a and the second outlet 292 b may also be formed as recesses. When the second inlet 292 a and the second outlet 292 b are formed as recesses, the second inlet 292 a and the second outlet 292 b may be opened on the mutually opposite sides.

As described above, even when the first decompression flow channel 291 c constituting the first decompression portion and the second decompression flow channel 292 c constituting the second decompression portion are formed in the recess shape instead of a slit, operational effects thereof may be the same. However, in case where the first decompression flow channel 291 c and the second decompression flow channel 292 c are formed in a recess shape as in this embodiment, rigidity of the gasket 291 constituting the first decompression portion or the back pressure plate 292 constituting the second decompression portion may be ensured. In particular, since the back pressure plate 292 supports the second scroll 250, it is required to have relatively high rigidity. When the second decompression portion 292 c is formed in a recess shape as in the present embodiment, higher rigidity may be advantageously ensured, as compared with the case where it is formed in the slit shape described above.

In addition, the third decompression portion according to the present embodiment may be formed to have a plate-like shape, like the first decompression portion or the second decompression portion. This plate will be defined as a decompression plate. FIGS. 11A and 11B are cross-sectional views illustrating other embodiments of the third decompression portion according to the present embodiment.

The decompression plate according to the present embodiment may be fixedly coupled to an outer surface of the main frame 102 as illustrated in FIG. 11A or may be provided between the main frame 102 and the main housing 111 as illustrated in FIG. 11B.

For example, when a decompression plate 293 is fixedly coupled to the outer surface of the main frame 102 as illustrated in FIG. 11A, a third inlet 293 a of the decompression plate 293 and a third decompression flow channel 293 c may be formed as recesses on the same plane and a third outlet 293 b may be formed as a recess on another plane or may be formed as a through hole.

Meanwhile, in case where the decompression plate is provided between the main frame 102 and the main housing 111 as illustrated in FIG. 11B, the third inlet 293 a and the third outlet 293 b may be formed as holes and the third decompression flow channel 293 c may be formed as a slit. Also, in this case, the third inlet 293 a, the third outlet 293 b, and the third decompression flow channel 293 c may be formed in a recessed shape. Also, in this case, the third outlet 293 b may be formed to communicate with the inside of the third decompression flow channel 293 c.

As described above, when the third decompression portion is formed in a plate-like shape, a decompression flow channel may be formed longer than the orifice, so that the decompression rate may be increased while hole of the decompression flow channel is formed to be wide. Accordingly, pressure of a gas oil discharged to the suction space from the back pressure space may be further lowered, thereby reducing suction loss in the suction space.

Hereinafter, another embodiment of the electric compressor according to the present disclosure will be described.

That is, in the above-described embodiment, pressure of the gas oil discharged from the back pressure space to the suction space is reduced by providing the third decompression portion formed as an orifice, a decompression valve or a decompression plate. However, in this embodiment, a fourth decompression portion may further be provided to further lower pressure of the gas oil discharged to the suction space.

FIG. 12 is a cross-sectional view illustrating another embodiment of a decompression device according to the present embodiment. As illustrated, the main frame 102 may include a third decompression portion and a fourth decompression portion which communicate with each other.

The third decompression portion may be configured by installing the orifice 193 in the discharge passage 125 as illustrated in FIG. 6, and the fourth decompression portion may be configured by installing a decompression plate on an outer surface of the main frame 102.

The inlet side of the decompression hole 193 a constituting the third decompression portion communicates with the back pressure space S3 and the fourth outlet 293 b constituting the fourth decompression portion communicates with the suction space S1, and the outlet side of the decompression hole 193 a may communicate with the fourth outlet 293 a constituting the fourth decompression portion through the communication hole 125 c. Accordingly, the gas oil in the back pressure space S3 flows into the decompression hole 193 a through the discharge passage 125 and moves toward the fourth decompression portion, during which the gas oil is reduced to a third pressure, and thereafter, the gas oil moves toward the fourth outlet 293 b along the fourth decompression flow channel 293 c constituting the fourth decompression portion, during which the gas oil is reduced to a fourth pressure, and is discharged to the suction space S1.

As described above, in the electric compressor according to the present embodiment, since the third decompression portion and the fourth decompression portion are provided side by side between the back pressure space S3 and the suction space S1, pressure of the gas oil in the back pressure space S3 is successively reduced while sequentially passing through the third decompression portion and the fourth decompression portion, and accordingly, pressure of the gas oil discharged from the back pressure space S3 to the suction space S1 may be further lowered.

Hereinafter, another embodiment of an electric compressor according to the invention will be described. That is, compared with the above-described embodiment in which both the first and second decompression portions and the second decompression portion is formed in a plate shape using the gasket and the back pressure plate, in this embodiment, one of the first decompression portion and the second decompression portion is formed in a plate shape and the other is configured as an orifice or a decompression valve.

FIG. 13 is a cross-sectional view illustrating another embodiment of a first decompression portion and a second decompression portion in an electric compressor according to the present invention.

As illustrated, in the present embodiment, the first decompression portion may be formed as an orifice 391 provided in the first scroll 140 and the second decompression portion may be formed as a back pressure plate 392 provided between the main frame 102 and the second scroll 150.

The first decompression portion may be formed to be the same as the third decompression portion (orifice) 193 illustrated in FIG. 6, and the second decompression portion may be formed to be the same as the second decompression portion (back pressure plate) 192 illustrated in FIG. 3.

In case where the first decompression portion is formed as the orifice 391 and the second decompression portion is formed as the back pressure plate 392 having an arc-shaped decompression passage as described above, the scroll depressed portion of the first scroll 140, since the orifice 391 is formed at the scroll side wall portion 142 of the first scroll 140 having a relatively large axial directional height, the orifice may be installed without having to increase the axial length of a member where the first decompression portion is to be installed. Accordingly, the first decompression portion and the second decompression portion may be configured as different types of decompression portions without increasing the axial length of the compressor.

Although not shown, the first decompression portion may be formed as a gasket having an arc-shaped decompression flow channel, and the second decompression portion may be formed as an orifice, respectively. In this case, the first decompression portion having a relatively low decompression rate is formed as the decompression flow channel having a circular arc shape, a decompression effect may be increased.

Hereinafter, another embodiment of the electric compressor according to the present disclosure will be described. That is, in the above-described embodiments in which the first decompression portion and the second decompression portion are formed on the gasket or the back pressure plate. However, in the present embodiment, the first decompression portion and the second decompression portion may be formed outside the gasket or the back pressure plate or may be formed in a recessed shape on a surface facing the members constituting the first position or the second position.

FIG. 14 is a cross-sectional view illustrating another embodiment of a first decompression portion and a second decompression portion in an electric compressor according to the present disclosure. As illustrated, the first decompression portion according to the present embodiment may include a first inlet 491 a, a first outlet 491 b, and a first decompression flow channel 491 c, as in the above-described embodiment. The first inlet 491 a is formed as a recess on a rear surface of the first scroll 140 so as to communicate with the oil supply hole 113 b, the first outlet 491 b is covered by the rear cover 113 and communicates with the first back pressure flow channel 142 a, and the first decompression flow channel 491 c is covered by the rear cover 113 and forms a passage having a circular arc shape. Accordingly, the discharge space S3 communicates with the first back pressure flow channel 142 a through the first inlet 491 a, the first decompression flow channel 491 c, and the first outlet 491 b.

Here, although not shown, the first decompression flow channel may extend from the oil supply hole 113 a and may be recessed on the front surface of the rear cover 113. Here, the first decompression flow channel may be covered with the first scroll 140 to form a passage having a circular arc shape.

The second decompression portion may be formed in the same manner as the first decompression portion. For example, the second decompression portion includes a second inlet 492 a, a second outlet 492 b, and a second decompression flow channel 492 c. The second inlet 492 a is recessed on a rear surface of the main frame 102 and communicates with an outlet side of the first back pressure flow channel 142 a, the second outlet 492 b is covered by the first scroll 140 and communicates with an inlet side of the second back pressure flow channel 121 a, and the second decompression flow channel 492 c is covered by the first scroll 140 and forms a passage having a circular arc shape. Accordingly, the first back pressure flow channel 142 a communicates with the second back pressure flow channel 121 a through the second inlet 492 a, the second decompression flow channel 492 c, and the second outlet 492 b.

As described above, the first decompression portion and the second decompression portion may be recessed on the facing surfaces of the existing members, i.e., the rear cover 113 and the first scroll 140 or the main frame 102 and the first scroll 140, without using a separate member, i.e., a gasket or a back pressure plate. Thus, the first decompression portion and the second decompression portion may be easily processed, and when the first decompression portion and the second decompression portion are formed, they are not restricted by a gasket or a back pressure plate, and thus, a degree of freedom of design with respect to the first decompression portion and the second decompression portion may be increased.

In the above-described embodiments, the main frame is separated and assembled with the main housing, but in some cases, the main frame may be integrally formed with the main housing. Also, in this case, the decompression device described above may be applied in the same manner. 

What is claimed is:
 1. An electric compressor comprising: a main housing including a motor chamber; a driving motor disposed in the motor chamber; a frame fixed to one end of the main housing; a first scroll supported by one side surface of the frame; a second scroll provided between the frame and the first scroll and supported by the frame, the second scroll forming a compression chamber with the first scroll, and forming a back pressure space with the frame, and configured to make an orbiting motion relative to the first scroll when receiving a rotational force from the driving motor to form; a rear cover coupled to the main housing to support one side surface of the first scroll and forming a discharge space with the first scroll; a back pressure flow channel extending through the first scroll and the frame and configured to guide a refrigerant and oil discharged from the compression chamber to the discharge space and the back pressure space; a first decompression portion provided at a first position between the rear cover and the first scroll, the first decompression portion being configured to reduce a pressure of the refrigerant and oil moving from the discharge space toward the back pressure space; and a second decompression portion provided at a second position between the first scroll and the main housing, the second decompression portion being configured to reduce the pressure of the refrigerant and oil moving to the back pressure space through the first decompression portion.
 2. The electric compressor of claim 1, wherein a decompression member having a plate-like shape is provided in at least one of the first position and the second position, and the decompression member includes an inlet communicating with an upstream side back pressure flow channel with respect to a movement path of the refrigerant and oil, an outlet spaced apart from the inlet and communicating with a downstream side back pressure flow channel, and a decompression flow channel connecting the inlet and the outlet, the decompression flow channel being configured to reduce the pressure of the refrigerant and oil moving from the inlet toward the outlet.
 3. The electric compressor of claim 2, wherein the inlet, the outlet, and the decompression flow channel extend through the decompression member in an axial direction.
 4. The electric compressor of claim 2, wherein at least any one of the inlet, the outlet, and the decompression flow channel includes a recess formed on one side surface of the decompression member.
 5. The electric compressor of claim 2, wherein the first decompression member positioned at the first position includes a sealing member having a portion positioned between the main housing and the rear cover.
 6. The electric compressor of claim 5, wherein the first decompression member includes a non-metal material.
 7. The electric compressor of claim 2, wherein the first decompression member positioned at the first position has an outer diameter smaller than or equal to an outer diameter of the first scroll.
 8. The electric compressor of claim 2, wherein a portion of the second decompression member provided at the second position includes a support member positioned between the frame and the second scroll.
 9. The electric compressor of claim 8, wherein an outer side portion of the second decompression member is fixed between the frame and the first scroll and an inner side portion of the second decompression member is configured to support the second scroll in an axial direction.
 10. The electric compressor of claim 1, wherein at least one of the first decompression portion and the second decompression portion is formed as a decompression flow channel having a predetermined cross-sectional area, the decompression flow channel including a recess formed on at least one surface of a respective one of the first position or the second position.
 11. The electric compressor of claim 1, wherein at least one of the first decompression portion and the second decompression portion is configured as a decompression flow channel formed in a slit shape on a decompression member provided at a respective one of the first position or the second position.
 12. The electric compressor of claim 1, further including: a discharge passage in the frame, the discharge passage extending between the back pressure space and the motor chamber; and a third decompression portion provided at the discharge passage, the third decompression portion being configured to lower the pressure of the refrigerant and oil discharged from the back pressure chamber to the motor chamber.
 13. The electric compressor of claim 12, wherein the third decompression portion includes a decompression member configured as one of an orifice or a decompression valve inserted into the inside of the discharge passage.
 14. The electric compressor of claim 12, wherein the third decompression portion has a plate-like shape disposed on one side surface of the frame, and the decompression member forming the third decompression portion includes an inlet communicating with the discharge passage, an outlet provided on one side of the inlet and communicating with the motor chamber, and a decompression flow channel connecting the inlet and the outlet, the decompression flow channel being configured to reduce the pressure of the refrigerant and oil moving from the inlet to the outlet.
 15. An electric compressor comprising: a main housing including a motor chamber; a driving motor disposed in the motor chamber; a frame fixed to one end of the main housing; a first scroll supported by one side surface of the frame; a second scroll provided between the frame and the first scroll and supported by the frame, the second scroll forming a compression chamber with the first scroll, and forming a back pressure space with the frame, and configured to make an orbiting motion when receiving a rotational force from the driving motor; a rear cover coupled to the main housing to support one side surface of the first scroll and forming a discharge space with the first scroll; a back pressure flow channel extending through the first scroll and the frame and configured to guide a refrigerant and oil discharged from the compression chamber to the discharge space and the back pressure space; and a plurality of decompression portions provided in the middle of the back pressure flow channel at predetermined intervals and configured to reduce a pressure of the refrigerant and oil moving from the discharge space to the back pressure space through the back pressure flow channel.
 16. The electric compressor of claim 15, wherein the plurality of decompression portions have different decompression rates.
 17. The electric compressor of claim 16, wherein a first decompression portion is provided between the rear cover and the first scroll, a second decompression portion is provided between the first scroll and the main housing, and a decompression rate of the first decompression portion is greater than or equal to a decompression rate of the second decompression portion.
 18. The electric compressor of claim 17, wherein the frame includes a discharge passage extending between the back pressure space and the motor chamber, the discharge passage further includes a third decompression portion configured to lower the pressure of the refrigerant and oil discharged from the back pressure space to the motor chamber, and a decompression rate of the third decompression portion is smaller than or equal to a decompression rate of the second decompression portion.
 19. The electric compressor of claim 15, wherein the plurality of decompression portions includes an inlet, an outlet, and a decompression flow channel connecting the inlet and the outlet, and the decompression flow channel may extend over an angle of at least 180° in a direction from the inlet to the outlet. 